Simon Cowell has admitted that he knew after a "millionth of a second" that One Direction could become massive.

Since leaving the X Factor in 2010, the boyband have gone on to achieve worldwide fame, with their recent sucess in America particularly impressive.

Speaking to Rolling Stone, X Factor supremo Cowell said that when he saw the newly formed band on the show on the judges' houses stage, he instantly knew something big was brewing. When asked when he thought the band could have massive potential, he replied:

"When they came to my house in Spain and performed, after about a millionth of a second. I tried to keep a straight face for a bit of drama for the show. I remember sitting next to this girl who I was working with. The second they left we jumped out of my chair and said, "These guys are incredible!" They just had it. They had this confidence. They were fun. They worked out the arrangements themselves. They were like a gang of friends, and kind of fearless as well."

Cowell added that he respected the band's artist vision whilst on the TV talent show. He continued:

"Once they were on the show, it was unusual because in an instant, we had hundreds of fans outside the studio. That doesn't happen very often. The more I got to know them, the more I liked them and the more I trusted them. They had good taste and they understood the kind of group they wanted to be. They didn't want to be molded. I'm not interested in working with people like that either."